Could you describe the conditions with a bit more detail?
For example, did you shut off your computer? If not, was the project open or closed the entire time? When you opened the project the second time, what had not been saved? Were the document titles on the left back to their defaults, or was it simply that when you clicked on the titles in the binder you didn’t see any text? Where was the file saved, on your hard drive, on an external drive, or a thumb drive?
I just realized that I opened either a snapshot or a backup - not the right version of the project. I wasn’t sure of the file naming convention and didn’t pay attention when I chose a save location to what I was doing. I’ve since located the correct file and now everything seems fine.